In a certain step in a mining process, water is extracted from wet ore material for washing out some undesired elements from the minerals, for example. This process step is carried out on an ore filter table. This type of filter is referred to as a horizontal ore filter. A plan view and an elevation view of a typical horizontal ore filter are illustrated in the accompanying drawings in FIGS. 1 and 2 respectively.
Examples of these filters are also described and illustrated in the following prior art documents:    U.S. Pat. No. 2,588,912 issued to H. W. Denhard on Mar. 11, 1952;    U.S. Pat. No. 2,798,612 issued to C. W. Crumb, on Jul. 9, 1957;    U.S. Pat. No. 3,080,063 issued to J. Krynski et al., on Mar. 5, 1963;    U.S. Pat. No. 3,361,262 issued to D. S. Orr et al., on Jan. 2, 1968;    U.S. Pat. No. 3,485,375 issued to G. Lee on Dec. 23, 1969;    U.S. Pat. No. 5,360,541 issued to M. Gerakios on Nov. 1, 1994.
A horizontal ore filter has a circular shape and its surface is covered by a series of filter segments 20, each having the shape of a sector of a circle. Each filter segment 20 is made of a perforated plate 22. The entire surface of the filter surface is covered by a filtering fabric 24 such as a canvas, a felt or another filtering material of the like. The filtering fabric 24 is made of a large piece covering several or all segments 20 at once. Generally, the filtering fabric 24 is attached to the filter segments 20 in a way that is illustrated in FIGS. 3 and 4, in the accompanying drawings.
Each filter segment has a channel 26 around its perimeter, and the filtering fabric 24 is retained to this channel by means of a rope 28 tucked into this channel 26. In many of the prior art models of horizontal ore filters, the channel 26 is welded, such as shown at 30, to a sub-frame 32 of the ore filter.
In use, a load of wet ore material is spread over the filter surface and a vacuum pressure is applied under the filter surface to extract water and fine particles from the ore material. The ore material is then picked up by a screw-type rotor and transferred to the next station of a treatment process. The operation of a horizontal ore filter is not further explained herein because this aspect of the ore filter is not the focus of the present invention.
It is known however, that the filter surface is exposed to friction wear due to the ore aggregate being spread there over and recovered therefrom in bulk by a rotor passing a very short distance from the surface of the filtering fabric. It is also known that generally, the entire filter surface must be renewed every six months or so, at a great expense. It is known that an overhaul of one of these filters requires the replacement of the filtering fabric 24 as well as the replacement of the channels 26 and the perforated plates 22 on some of, or on all the filter segments 20.
The replacement of the filter segments 20 of the prior art consists of pulling the rope 28 from the channels 26; removing the filter fabric 24, and then gouging out the welds 30 from the damaged perforated plates 22 to separate the plates from the sub-frame 32. This work is done by workers standing on the structure of the filter.
The pulling of the rope 28 is particularly dangerous, because the rope 28 often breaks or give away suddenly, thereby causing the person pulling on it to become out of balance and to fall down from the structure of the filter. The filtering fabric 24 can also be stuck to the perforated plate and give away suddenly when it is pulled up, also causing accidents. Therefore, the replacement of filter fabrics from the filter surface is a difficult and dangerous task. Moreover, the overhauling of the filter surface keeps the machine out of service for an extended period of time.
One difficulty in finding a safer and more productive method for fastening the filtering fabric to the surface of the ore filter is that the rope-and-groove method of the prior art is very effective in sealing any gap between adjacent surface sectors. The efficiency of the filtering process depends on an airtight mounting of each surface segment to the sub-frame of the ore filter. Therefore the obtainment of a better airtight mounting of each surface sector in particular, using a different structural configuration, has been a challenge in the past.
In some instances, such as the ore filter described in the U.S. Pat. No. 3,361,262 mentioned before, independent segments are made with the aforesaid channel extending all around. These segments are removably mounted to a sub-frame. The segments are bolted at both ends to the sub-frame. Caulking is placed between the sectors of the filter surface to provide a seal across the filter surface.
These segments are subject to vibration, and because they are only supported from underneath along their lengths, theses vibrations cause vibration waves to travel there along. These vibration waves cause accelerated wear on the fabric material for reducing the gap between the filter fabric and the equipment overhead. These vibration waves also cause a loss of vacuum under the filtering surface, and between the filter segments, when the caulking material between the segments has hardened and cracked for example.
Although there is a need in this market for a safer procedure to replace worn-out filtering fabrics, any new method must encompass a structure that provides a good seal across the entire filter surface. The sealing aspect of an ore filter having replaceable filter segments is the main focus of the present invention.